What Will Dawn Find At Ceres?

By David Darling

The Dawn spacecraft has left Vesta and is currently on its way to Ceres, which it should reach in 2015. Image Credit: NASA

NASA’s Dawn spacecraft was launched September 27, 2007, on a unique mission: to explore the two most massive objects in the asteroid belt, Vesta and Ceres. Propelled by an ion engine, it will, if successful, break new ground in spaceflight by becoming the first probe to orbit two separate extraterrestrial bodies.

Dawn’s journey to Vesta took almost four years and involved a flyby of Mars, to get a gravity assist, and several extended periods of ion engine thrusting. On July 16, 2011, it entered orbit around the potato-shaped, 525-kilometer-wide Vesta for a detailed study of the asteroid lasting more than a year. On September 5, 2012, it fired its thrusters again to break free of Vesta’s gravity and began the long haul to its next target—the dwarf planet Ceres.

Ceres is by far the largest body in the asteroid belt and the first to be discovered, by Guiseppe Piazzi in 1801. It measures 950 km (590 miles) across and, as distinct from almost every other asteroid, is round like a planet, its self-gravity having been strong enough when it was still molten to pull it into a spherical shape. In 2006, it was given dwarf planet status by the International Astronomical Union, putting it in the same category as Pluto.

Dawn’s next stop—the dwarf planet, Ceres. Image Credit: NASA

The Hubble Space Telescope has captured images of Ceres revealing a dozen or so large, fuzzy features, some of which are craters. But Dawn will provide us with the first clear pictures of a dwarf planet—five months before New Horizons sweeps past Pluto, opening our eyes to that small world as well.

Dawn is scheduled to go into orbit around Ceres in February 2015, starting out at an initial altitude of 5,900 km. After five months at that height, the spacecraft will spiral down to a lower orbit 1,300 km high, and then, after another five months, down to a minimum orbit taking it to within just 700 km of the surface.

Dawn’s main goal, as at Vesta, will be to shed light on the early history of the solar system and the process by which planets are formed. These most massive of asteroids are perfect for this objective because they’re the largest surviving protoplanets that we know about—and quite different in character. Whereas Vesta is mainly rocky and highly evolved in a geological sense, Ceres is icy and more primitive, a result of them having formed at different distances from the Sun.

Dawn’s instrumentation includes a framing camera, a visual and infrared spectrometer, and a gamma-ray and neutron detector. These will be trained on the dwarf planet to determine its exact shape, the nature of its topographical features—down to a resolution of about 60 meters per pixel (a vast improvement on the 18 km per pixel available with Hubble)—and the composition of its surface.

The end of Dawn’s primary mission is scheduled for about July 2015, and after that an extended mission is possible which could involve further study of Ceres or moving on to a third object in the asteroid belt. Originally, Pallas, another giant asteroid, was considered as an extended target, but delays in launching Dawn have probably put it out of range. A limited fuel supply for its ion thrusters may make it impractical to break orbit from Ceres, and the spacecraft may end its days continuing to send back information from a few hundred kilometers above the dwarf planet’s surface.

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10 comments to What Will Dawn Find At Ceres?

Apparently Jim Hillhouse has once again accurately predicted impending action on The Hill when he stated several weeks ago that the Administrations proposal to “lasso an asteroid” was DOA. According to the Daily Launch of the AIAA 17 June, the House Science, Space, and Technology Committee has begun drafting a NASA authorization bill that would “bar funding for a planned asteroid rendezvous mission.” The Space subcommittee plans to hold a hearing Wednesday.

On the House Appropriations side, there seems to be little enthusiasm for the asteroid mission. Unless the Senate digs in its heels on funding the asteroid mission, this one is done.

It appears that House Space Committee chair Rep. Lamar Smith threw a bone to Rep. Bernice Johnson in supporting an additional $175 million to commercial crew. I think he did this knowing full-well that the appropriators on the Senate side, never mind his own appropriators in the House, are unlikely to vote that way.

Actually Jim, I was pleasantly surprised to see an elevated funding for Commercial Crew on the draft House bill. Commercial manned access to the ISS should begin as soon as it’s possible, cause it would be a ‘waste’ in the current financial environment, IMHO to use SLS just to go the ISS. If that were to happen, it would give just another reason for the anti-SLS tree-hugging fanatics to howl against the SLS, which is obviously a system suited for BEO.

Leonidas, it’s always a pleasure to read your posts, and I wish you well (especially with all that is going on in neighboring Turkey – keep your head down Leonidas! 🙂 Jim is far, far more knowledgeable about the political climate our space program must fight to survive in, but I believe the draft bill also includes an increase for missions of planetary exploration, and with the dire economic circumstances we find ourselves in (which, being Greek, you are very familiar dire economic circumstances) if it is a choice between more money for CommSpace or funding planetary science and exploration, I would choose funding for our planetary exploration missions. Best wishes and highest regards!

Thank you Karol for all your nice words! It’s always a pleasure to read your posts as well 🙂 Actually Greece is already in flames-Turkey’s recent fighting doesn’t come close I think. Financial climate? I’m 18 months in the unempoyment line and counting. Unemployment rate is currently 27% and rising every month (in the age group of 18-25, 60% are unemployed). Any job opportunities abroad anyone?

Anyway, that’s not the issue here. Speaking of planetary science exploration, the Planetary Society is recently in a battle about the planetary science cuts. But they are shamelesly over-hyping the whole thing and their ‘end of the world’ rhetoric annoys me. The don’t put the whole thing in context and their acting like NASA is their pet funding agency. Not to mention their rather anti-manned approach to space exploration I object to. When my subscription expires, it will be a long long time until they’ll see me again.

The reason I’m behind Commercial Crew, is that it will free up NASA’s resources for going beyond LEO. It would be a very sad sequence of events, having NASA to develop SLS just to send astronauts to the ISS (and then we’ll hear more of the anti-SLS rhetoric that has grown tired really).

Sure, send the private sector to ferry people to the ISS. I don’t have a problem with that. It may help develop a commercial market in LEO in the long run. That’s a win-win for everyone. If the funding is limited NASA will have to choose between LEO and the Moon and Mars. So, free up NASA’s funding by having the private sector do all the LEO stuff, and let NASA explore beyond.

And I sure love robotic exploration! I’d also like to see a probe to Europa. But if developing the manned infrustructure means we have to postpone Europa for a while, well, I can live with that!

I wouldn’t read too much into the possible increase in commercial crew funding in the authorization bill. Things in politics are rarely what they seem.

The people who actually fund programs, the appropriators, will likely not fund commercial crew to a level anywhere near $700m. The appropriators feel that NASA has sufficient resources for commercial crew if the space agency’s leadership would only do what it rarely does, make tough choices. Appropriators have been emphatic that NASA pare down the number of commercial crew participants to match that program’s funding.

Thank you very much Jim for the clarification! You are on the inside of things and you can know better, I’m just commenting on what I read.

So, is it the case then that NASA leadership wants more money for Commercial Crew in order to develop all three commercial proposals (Boeing, SpaceX and SNC), while Congress says that enough money are there for the development of just one?

Don’t you all think that the funding for the Asteroid is going to emerge…Wasn’t that thing in Russia a wake up call to the entire planet?… NASA did just name the astronaut crew for the mission… Bechtel did just join Planetary Resources…Musk just announced no IPO for SpaceX until after the Mars Transport Vehicle is operational …looks like all the stars have aligned and the people in the know …Know we better get going because the big one may be on to us before we see it coming! Hope were not to late!

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